The present invention relates in general to a mudsaver valve and particularly to a mudsaver having a rotating ball valve with snap-action for both opening and closing the valve.
Mudsaver valves, mounted on the bottom of the drilling rig kelly or top drive, serve to automatically retain drilling mud within the kelly or top drive and its supply hoses and tubing whenever the kelly or top drive is disconnected from the drillstring. The kelly or top drive is routinely disconnected to add or remove pipe from the drillstring.
Retention of drilling mud is desirable in order to avoid the loss of expensive mud, as well as the creation of slick and hazardous working conditions and the resultant loss of time due to rig floor cleanup. The mudsaver functions as a type of relief valve. Whenever the mudsaver is closed, it must support the hydrostatic head of the noncirculating fluid trapped above the mudsaver when the drillstring is separated from the mudsaver. However, when the mudsaver is reconnected in the drillstring, the valve must readily open when the mudpumps are started.
Several previous designs of mudsaver have been created and used, as is discussed below. However, most such designs have had significant drawbacks and are not widely used in the oilfield. Two very significant drawbacks to all of the designs reviewed below is their susceptibility to wear from abrasive fluids and their complex assembly. Partially open valves, particularly ball valves, experience significantly worsened fluid-induced wear rates. This is especially true when used with drilling mud, which is highly loaded with abrasive particles.
In fact, current mudsaver designs are so unsatisfactory that typical operations will retain the mud within the kelly or top drive by manual closure of a valve at the lower end of the kelly, called the kellycock. This situation is highly undesirable because the lower kellycock is a critical drilling safety component intended for occasional or emergency use. In addition, an actuator and its controls must be provided and maintained for the operator to close and open the lower kellycock. Thus, the provision of a suitable autonomous mudsaver would preserve the lower kellycock for its intended safety purposes.
The mudsaver described in U.S. Pat. No. 3,965,980 is one attempt to solve the problems set forth above. The valve described is basically a poppet relief valve. The poppet is spring-biased closed and is opened when drilling mud pressure acting on one side of the piston on the upper end of the sealed spring chamber exceeds the combined resistance of the biasing spring and the counter pressure within the sealed spring chamber. The poppet valve has a check valve mounted concentrically within its head to permit communication of mud pressure from below through the closed poppet for measurement above the mudsaver. Flaws in the design of the valve are its length, multiple-part outer body, difficult assembly and disassembly, and that its sealing plug and seat are subject to high erosion and attendant leakage due to mud circulation impinging both components. Drilco Inc. (a division of Smith International, Inc.) of Houston, Tex. markets the patented valve and SMF International of France markets a similar valve.
U.S. Pat. No. 3,743,015 describes another approach. This mudsaver has a rotatable, translatable ball sealing plug with a through hole. The valve is actuated by differential pressure across an annular piston. On the upper side of the piston, pump pressure acts, while on the other side, a biasing chamber provides a reference pressure (typically atmospheric). The ball is further urged toward its closed position by biasing springs. A means of locking the ball open by means of an externally operated wrench permits wireline operations through the valve. Drawbacks of the valve are the potential leakage paths through the side of its body, high operating forces on the valve with rapid increases in pump pressure or water-hammer, and an involved assembly and disassembly of the large number of parts positioned in crossbores.
A further approach is found in U.S. Pat. No. 4,262,693 which discloses a mudsaver based upon a rotatable, nontranslatory ball sealing plug with a through hole. This valve appears to be substantially similar to the mudsaver marketed by Arrowhead Continental, San Bernardino, Calif. An actuation piston is exposed to pump pressure on one side and a second bias pressure in a sealed spring chamber plus a biasing spring force on the second piston face. A net differential pressure causes axial movement of the actuation piston. The actuation piston is coupled to a rotator sleeve by means of one or more piston-mounted camming pins acting in one or more helical grooves in the rotator. Accordingly, axial movement of the piston imparts rotary motion to the rotator, which in turn rotates the ball by means of bevel gears. This mudsaver has relatively high frictional loads and multiple interacting parts.
Yet another approach is seen in the mudsaver valves offered by American International Tool Company, Inc. and A-Z International Tool Company. Their mudsavers retain the mud above the valve by comating annular flat sealing faces transverse to the mudsaver axis dividing an upper annular fluid path from a lower central fluid path. The flat faces are spring-biased together to remain in a closed position under non-flowing mud when the drillstring is separated. The lower flat sealing face constitutes a piston head which is exposed to the pressure above the sealing face on its upper side and the pressure downstream of the annular orifice between the sealing faces on the other side. Pump pressure is sufficient to overcome the spring bias and then the pressure drop across the annular orifice will maintain the valve open. This mudsaver has a coaxial poppet check valve to permit communication of pressure below the valve past the primary valve seal. The primary disadvantage of this valve is the tendency of the sealing faces to wear under direct flow impingement.
U.S. Pat. No. 5,509,442 discloses another mudsaver based upon a rotatable, nontranslatory ball sealing plug with a through hole. An actuation piston is exposed to pump pressure on one side and atmospheric bias pressure in a spring chamber plus a biasing spring force on the second piston face. A net differential pressure causes axial movement of the actuation piston, which in turn can cause valve shifting if permitted by an interlock system controlled by the presence of the abutting end of the drillstring below the valve. The tool is relatively long and has a jointed body which makes assembly and disassembly difficult.
U.S. Pat. No. 4,248,264 discloses a flapper valve-based mudsaver. The flapper is normally biased closed both by gravity and by a torsion spring. The flapper is mounted on an upwardly spring-biased piston ring concentric with the flow passage. Atmospheric pressure is retained within the spring chamber below the piston. When pump pressure forces the annular piston carrying the flapper valve and its seat downwardly, the flapper encounters a fixed annular tube concentric within the valve seat and passing through the annular piston. This unseats the flapper, permitting flow. Pressure from below will either unseat the flapper or, if it is already open, not permit the piston to travel to a position where the flapper will seat. If there is no pressure overcoming the spring bias, the piston moves up against the pressure of the retained mud and closes. This valve gradually opens and closes and is susceptible to wear. Furthermore, pressure surges produce high loadings on the flapper hinges.
U.S. Pat. No. 4,889,837 discloses a poppet-type mudsaver in which the poppet is restrained against downward movement by an integral spider which abuts a stop shoulder. The poppet seat is a spring-loaded annular piston which translates away from the poppet when the pump pressure exceeds the atmospheric pressure acting on the piston area and the spring preload. The poppet is free to reciprocate upwardly if there is pressure from below the closed valve. This valve is not full opening, so it is subject to flow abrasion.
As pointed out above, a mudsaver is subject to tremendous wear from the abrasive particles in the mud. Currently, all of the mudsaver valves open and close in the traditional manner, where the valve is partially open during the opening and closing of the valve leading to rapid wear of the valve.
Several downhole safety valves have attempted to limit wear by incorporating a valve that opens or closes in one rapid movement (a xe2x80x9csnap actionxe2x80x9d valve). For example, U.S. Pat. No. 3,749,119 discloses a valve reopening operator sleeve retained in either an upper position or a lower position by the engagement of annular latch grooves with an annular garter spring. Although closure of the main valve is not impacted by the sleeve, the reopening of the valve is. Shifting of an independent inner sleeve mounted within the valve reopening sleeve downwardly to a first position permits closing an activator valve at the upper end of the reopening sleeve. The closure of the activator valve permits the reopening sleeve to be pumped downwardly from its upper position to its lower position to force open the main valve. The reopening sleeve is disengaged from its lower position by independent upward movement of the main control sleeve. The main valve and the activator valve are both flapper valves and are both spring-biased closed. The garter spring does not cause snap action in this application, but rather serves as a releasable retainer on a secondary operator.
U.S. Pat. No. 3,070,119 (xe2x80x9cRaulinsxe2x80x9d), U.S. Pat. No. 3,126,908 (xe2x80x9cDickensxe2x80x9d), and U.S. Pat. No. 3,889,751 (xe2x80x9cPetersxe2x80x9d) all disclose valves using latches for snap action. Raulins has a latch based on spring-loaded balls which act directly on the sealing poppet of the valve to provide snap action closure only. The sealing poppet of the valve is loaded by pressure drop across an integral internal flow beam. This load is supported by an annular array of balls which are spring-biased inwardly to engage a shoulder on the sealing poppet. The biasing load on the balls is provided by a very large axial force from an axially-acting coil spring bearing on a conically tapered ball support ring. The snap action is only in one direction and is actuated by forces applied to the sealing member, rather than an independent actuation mechanism.
The Peters apparatus is similar to that of Raulins, but the latch arrangements differ. Peters permits the sealing plug to move a limited amount prior to closing and uses axially translating balls that shift from one groove to another to release. Raulins permits substantially no sealing plug movement prior to latch release and does not use axially translating balls. The Dickens apparatus relies on an actuator with either a collet latch or ball latch released by movement to a disengagement groove under flow forces. A lost motion mechanism is required to link the actuator to the valve in order to accommodate the movement without affecting valve position. A very high axial bias force on the latch mechanism is required. The valve closing and opening require high flows to occur, so that reliable snap action is not a certainty with this device.
U.S. Pat. No. 4,160,484 discloses a flapper-type valve in which the flapper is biased to be normally closed, but is held open by a tube latched by a collet mechanism which releases at a predetermined load. The valve functions independently of the tube when the tube is not in position to paralyze the valve. The collet serves only to retain the tube in position and the latch does not provide for snap action.
All of the described devices either have a sealing plug directly loaded and held against closure until a predetermined release load is obtained or they rely upon a lost motion mechanism to effect closure. Not one of these devices has a reliable bi-directional snap action.
Thus, a need exists for a mudsaver valve that is less susceptible to abrasive wear to provide long life and reliability. In addition, a need exists for a mudsaver valve that can be adjusted to accomodate variations in mud weight and is short in length and easily assembled and disassembled.
The invention contemplates a simple device for solving the problems and disadvantages of the prior approaches discussed above. The mudsaver valve of the present invention provides a mechanism for a quick, automatically operating, snap acting opening and closing mechanism which is resistant to wear.
One aspect of the invention provides a reliable set of means for causing the combination of a valve operator and a valving member to exhibit bi-directional snap-acting behavior in the opening and closing actions of the combination.
Another aspect of the invention provides a reliable means of causing bi-directional snap-acting behavior in which the effecting bistable mechanism acts directly on the valving member.
A further aspect of the invention provides a means for inducing bi-directional snap-acting behavior in a valve operator and valve member combination in which the valving member is a rotary ball valve.
An additional aspect of the invention provides an automatic, full-opening, ball-type mudsaver valve with snap-acting opening action, as well as snap-acting closing action.
Yet another aspect of the invention provides a mudsaver valve which readily communicates drillstring pressure below the valve to above the valve without operator intervention.
A further aspect of the invention provides a mudsaver valve for which the sealing ball plug is automatically unseated in the event of very rapid mud pump pressure buildup or waterhammer, so that operating friction is reduced.
In addition, this invention provides a mudsaver valve which can be readily adjusted for changing mud densities.
Yet another aspect of the invention provides a mudsaver valve which is simple to assemble and disassemble under field conditions.
A further aspect of the invention provides a mudsaver valve, adapted for connecting a kelly or a top drive and a string of drill pipe, having a tubular valve body with a through bore flow passage, the body configured to connect to a drill string at its lower outlet end and to connect a kelly or a top drive at its upper inlet end. The mudsaver valve has a nontranslating rotatable ball with a through hole, where the ball is rotatable between a first and a second end position about coaxial central pivot pins journaled by a ball cage, such that when the ball is in the first position the ball through hole is aligned with the bore flow passage and when the ball is in the second position the ball through hole is misaligned with the bore flow passage to prevent flow through the valve. The valve has a valve seat that seals against the lower side of the ball and a dirt excluder that seals against the upper side of the ball. The valve has a reciprocable camming means for rotating the ball between the first and second end positions, a detent means that interacts with the ball to retain the ball in either end position until sufficient force is applied to the ball to overcome the interaction of the detent means with the ball, and an actuating means
for displacing the camming means to rotate the ball, where the actuating means is responsive to valve inlet pressure on a first face and other forces on a second face that is obverse to said first face. Thus, when the actuating means applies sufficient force to the camming means to overcome the interaction of the detent means with the ball, the ball will rotate from one end position to the other end position.
The foregoing has outlined rather broadly several aspects of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed might be readily utilized as a basis for modifying or redesigning the structures for carrying out the same purposes as the invention. It should be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.